Proteoglycans (PGs) are conjugates of glycosaminoglycans and proteins. No precise biological role has been assigned to these substances, but they are thought to be involved in cellular adhesion and in the maintenance of the integrity of the extracellular matrices. We have continued our studies on cell surface PGs by isolating them and studying their distribution and interactions with other macromolecules. During the past year, we have shown that a chondroitin sulfate proteoglycan from rat yolk sac tumor cells inhibits the attachment of cells to fibronectin and type I collagen matrices, suggesting that this proteoglycan may play a role in the reduced adhesiveness of the cells producing it. We have also isolated cDNA clones for the core protein of this proteoglycan, using as probes oligonucleotides synthesized on the basis of amino acid sequence information. The cDNA will be used to determine the entire amino acid sequence for the core protein. Antibodies will be prepared against synthetic peptides modeled after the predicted amino acid sequences. Antibodies that are reactive with the native proteoglycan will be used to study the distribution of the proteoglycans in normal and malignant cells and tissues. These new approaches will help clarify the role of the chondroitin sulfate proteoglycans in the assembly of extracellular matrices together with fibronectin, collagens, and other matrix proteins and as modulators of the cell adhesive properties of such matrices. (A)